Weighing up Button's McLaren move
Button joins Lewis Hamilton in an all-English line-up that will have those watching F1 salivating. Some will be attracted by two such appealing figures in the same team - not to mention the glamour that will be provided by their respective girlfriends. Others will be fascinated to see how the two drivers match up on the track.
And that is where the risks for the McLaren new boy are immense, even though Button has seven years' more experience than his new partner.
As I explored in my blog on Monday, Hamilton is considered by many observers to be the fastest driver in F1. Button may be the reigning world champion, but he has not yet proved to be quite in the same league as Hamilton, or the new Ferrari driver Fernando Alonso.
The issue is not Button's pure pace when everything is to his satisfaction. At times like that, there are few, if any, faster than him, as he proved with his glorious run to six victories in the first seven races of 2009, the foundation of his title campaign.
The problem Button will face is that, as one former F1 driver put it on Wednesday: "He needs a perfect car - that's been obvious throughout his career."
When he is not happy with his car, Button can struggle - and Hamilton provides a sterner challenge than any of his team-mates so far.
Complicating the issue at McLaren next year will be that Hamilton and Button like very different things from their racing cars.
The fates of Button, Hamilton and Raikkonen have become inextricably entwined
Hamilton likes a rear end that moves around a lot - he uses the rapid change of direction that provides to pitch him quickly into the corner and get him pointing in the right direction for the exit as soon as possible.
It is an unusual style, for the simple reason that it makes the car unstable - but Hamilton does not worry about that, he simply corrects the slide he knows is coming and carries on.
Button's style is completely different. He likes a stable rear end, using subtly changing pressure on throttle, brake and steering to alter the car's direction. Give him a loose rear end, and he struggles.
Can McLaren provide two cars set up in such different ways? Even if they can, will they want to, given the two varying development paths to which each approach may lead?
These concerns might sound esoteric to the average sports fan, but they are absolutely critical to an F1 driver's performance on the track. And that is why so many observers worry for Button at McLaren.
Button himself is obviously not concerned - he surely would not have signed up if he was. Underneath that laid-back exterior is a highly competitive man who clearly thinks himself more than capable of handling whatever Hamilton can throw at him. Only time will tell if he is right.
Just as fascinating is how the world champion has ended up leaving the team with whom he won the title.
This situation carries echoes of 1996, when Damon Hill lost his Williams drive despite becoming world champion.
Hill was only left with scraps after Williams told him late in the day that he would not be keeping him, and he ended up 'defending' his crown in an Arrows-Yamaha. Predictably, it did not go well.
Button, by contrast, has been the master of his own destiny, and he appears to have plumped for what he believes will be the most competitive car - a decision presumably based on McLaren's strong end to the season and Brawn's dip in competitiveness, as well as, he revealed on Wednesday, his new team's historic position as one of F1's few consistent success stories.
A bigger question hangs over how Button's former team have managed to let the man who won them their first world title slip through their fingers.
That is a complicated question, the answer to which at least partially lies in Mercedes's takeover of Brawn, which was announced on Monday.
There are lots of conflicting rumours doing the rounds. The most common one is that Brawn/Mercedes did not offer Button the salary he wanted, and that he preferred both McLaren's offer, and what he perceived to be a likely more competitive car.
But some media outlets have quoted "Brawn sources" saying they were offering Button £10m, which is almost certainly at least as much as he will get from McLaren.
Equally, there are rumours that Mercedes, the new owner of Brawn, was not that bothered whether Button stayed or not - and that, to keep the unions and anti-F1 members of the company's board happy, they were not prepared to offer him big money.
This is in the context of Mercedes's decision to end their part-ownership of a perfectly good F1 team to take a bigger share of another.
As ever, F1 is a tangled world - and that extends to another piece of news that broke on Wednesday.
Kimi Raikkonen, the 2007 world champion, will not be racing in F1 next year having failed to reach an agreement with McLaren.
The fact that the Finn could not finalise a deal with a team that made moves to sign him as long ago as August is at least partly down to the fact that Raikkonen wanted more money than McLaren were prepared to pay.
Raikkonen is being paid millions of pounds not to drive for Ferrari next year after the Italian team decided they preferred to have Alonso.
Yet it seems Raikkonen was determined to be paid what he and his management team deemed a wage reflective of his status as a former world champion - and the deal fell down because, while McLaren were offering the Finn a very substantial salary, it was not what Raikkonen had in mind.
As Raikkonen's manager David Robertson put it to me this morning: "It wasn't in his interests to race for the sum they were offering."
For now, Raikkonen and Robertson are viewing it as a year away from F1 to have some fun in the world rally championship. But, unless Raikkonen shifts his expectations, it may well turn out to be a rather more permanent arrangement than that.
F1 might not miss Raikkonen's android-on-Mogadon news conferences, but the man behind the wheel is another matter.
When he is in the mood, Raikkonen is one of the very finest drivers in F1 - arguably, with Hamilton and Alonso, one of only three who can win a race in a car that does not deserve to.
For a driver of that calibre to slip out of F1 in such an unsatisfactory manner is sad indeed. Hubris can be a dangerous thing.